Understanding the electrical components on the carby of a '92 GQ RB30.

[ThinkandBuild]

Team, I'm trying to track down an odd starting issue that only affects the vehicle when it is parked facing uphill on a reasonably steep slope. To this end I'm checking the in-tank fuel pump delivery circuit.

I've tried to run the fuel pump by turning the ignition key on to IGN, or the engine running position after starting. I had read that in this position the fuel pump should energise and deliver fuel to the filter. It doesn't!

Reading some more, it seems there is another switch in the circuit that controls when the fuel pump runs. Since the vehicle runs fine once started, and starts perfectly except when on steep uphills, the pump does work, so there must be a switch somewhere that determines when it runs.

Looking at the carby, there are three devices on the carby that have wires running to them, so perhaps one of those is the trigger I'm missing. I've read oen might be a heating element for cold weather starting, and that it can be isolated if need be.

So, my initial goal is to have a better understanding of what these three electrical devices are, and if one of them does indeed switch the pump, I would like to know which and verify its operation.

My ultimate goal is to make the vehicle start well on any slope, and my gut feel right now is fuel or carby, because nothing else mechanically or electrically really gives a toss if the vehicle is horizontal or otherwise.

I had hoped to measure the fuel flow rate and delivery pressure at the fuel filter when the vehicle was uphill and horizontal, hence my desire to get the fuel pump running on just the key switch rather than when the engine is running.

I have read on here about a solenoid in the fuel return line that is RPM activated, but my return path doesn't seem to have such a device fitted, or at least not in the location discussed, ie near the grille on the driver's side.

A bit more detail is that I can start the vehicle on a hill, but if I don't rev the crap out of it for 30 seconds, the moment I let the revs subside, the thing stalls and is a bugger to start for the next 30 minutes. I'm thinking it starts well off the fuel in the float bowl, but that fuel is not being replaced without a tonne of revs.

I've tested the pump by putting 12V to it directly and it flows fuel. I've blown out the supply line to the filter and it is clean. It doesn't starve for fuel when driving, so I don't believe I have a blocked fuel filter or lines.

Any help would be greatly appreciated. Not having 25 posts or more yet, I'm not allowed to download the manuals (admin rule) so I'll try and soldier on with your input and a bit more trial and error.

As a last resort I'm thinking of doing the EFI from a VL upgrade, but that too requires a switch for the fuel pump, so I may as well get my head around this control system for my own use now and in the future.

Cheers.

[mudnut]

Hello and welcome to the forum.

This thread; http://www.nissanpatrol.com.au/forum...-Helpful-Hints

has some RB30 specific info which might help.

Slip over to the introductions and tell us a bit about yourself and your Patrol. Greet 24 new members and you can download the manual.

[4bye4]

G'day mate and welcome to the forum. Can't help with your problem, but suggest you may like to go the the introduction thread and post an introduction and tell us a bit about yourself. This will also get you 1 step closer to the 25 posts.

[ThinkandBuild]

Mudnut, it was one of your contributions that let me know that my sort of diagnosing engineers lived in these electronic woods.

[Throbbinhood]

A bit more detail is that I can start the vehicle on a hill, but if I don't rev the crap out of it for 30 seconds, the moment I let the revs subside, the thing stalls and is a bugger to start for the next 30 minutes. I'm thinking it starts well off the fuel in the float bowl, but that fuel is not being replaced without a tonne of revs.

This is a common problem with the rb30 carbies. While I don't often start it on big angles, it will certainly stall if I'm on a steep incline and stop for whatever reason. If I keep moving, that is, there's some vacuum or whatever it needs to keep the fuel being sucked into the float bowl, it's no issue. I don't even have to be moving fast, idle rpm's but with the foot down a bit to keep moving up the hill is all she needs, but as soon as I let off the gas for more than a few seconds she'll stall. Cranking her over with my foot down is normally enough to get her going again - but it does make winching steep uphills a pain as it can mean riding the clutch a fair bit (my gearing's out with 35s).

So yeah, I don't have much in the way of a solution for you other than to EFI it - I haven't bothered as it hasn't presented that much of an issue to me - but I'd say this is the most likely cause of your problem.